The present inventive subject matter relates to information storage devices and methods of operating the same, and, more particularly, to information storage devices using magnetic domain wall movement and methods of operating the same.
In general, examples of conventional nonvolatile information storage devices in which recorded information is retained even when power is cut off include hard disk drives (HDDs) and nonvolatile random access memories (NVRAMs).
An HDD is an information storage device having a rotating part that may wear down over time. If the rotating part of an HDD wears down, an operational failure is likely to occur, thereby lowering the reliability of the HDD. A representative example of a non-volatile RAM is flash memory, which has come into widespread use. However, flash memory generally has relatively slow reading and writing speeds, a relatively short life span, and relatively small storage capacity when compared to an HDD. Flash memories may also have relatively high manufacturing costs.
To solve the problems of such conventional non-volatile information storage devices, new information storage devices that use the principle of magnetic domain wall movement of a magnetic material (hereinafter referred to as “magnetic track memory”) have been developed. In these magnetic information storage devices, a minute magnetic region formed of a ferromagnetic substance is referred to as a magnetic domain and a boundary portion between magnetic domains having different magnetization directions is referred to as a magnetic domain wall. The magnetic domains and the magnetic domain walls may be moved by applying current to a magnetic layer.
An information storage device using magnetic domain wall movement detects a desired location by moving a domain of a magnetic track and writes data to or reads data from the detected location. For example, in an information storage device that uses a U-shaped magnetic track, a plurality of magnetic domains are consecutively arranged within the U-shaped magnetic track and magnetic domain walls are respectively disposed between adjacent magnetic domains. Writing or reading is performed using a write unit or a read unit while moving the magnetic domains and the magnetic domain walls.
However, in the case of such an information storage device using a U-shaped magnetic track, only half the U-shaped magnetic track is used as an effective storage region, and thus, it may be difficult to store a large amount of information therein. Also, it may take a lot of time to perform addressing on such an information storage device, because location information is received from the outside, the location information is decoded, and a domain of a magnetic track is moved according to the decoded location information. Also, it may be difficult to secure a sufficient sensing margin for reading data. That is, to obtain a high-quality memory device, the memory device is typically required to be capable of storing a large amount of data in a small region thereof and writing/reading speeds of the memory device may be required to be as high as those of dynamic random access memory (DRAM). However, conventional information storage devices using magnetic tracks typically do not satisfy all the above requirements.